Hi there. I know how important it is to be able to delete transactions in QuickBooks Self-Employed. In the article linked above by JamesM, the steps are listed that explain the process of deleting a transaction in QuickBooks Self-Employed.

Here they are again in case you missed it: 

If you access QBSE through a web browser

1. Open the transaction from the Transaction page.
2. Select the transaction.
3. Select Delete, then choose Yes to confirm.

If you access QBSE through the mobile app

1. Tap the transaction.
2. Tap Delete Transaction.
3. Select Yes to confirm.

If you have any other questions or concerns, please reach out to the QuickBooks Self-Employed team directly. This team specializes in the Self-Employed product, and they'll be able to get you back on track.

Have a nice day.